Magnetic field cancellation circuitry

ABSTRACT

An apparatus includes at least one first circuit configured to generate a first time-varying magnetic field for magnetic induction power transfer to a device, at least one second circuit configured to generate and/or receive a second time-varying magnetic field for magnetic induction data transfer to and/or from the device, and at least one third circuit configured to generate a third time-varying magnetic field in response to a time-varying electric current. The third time-varying magnetic field is configured to at least partially inhibit degradation of said data transfer from the first time-varying magnetic field. The apparatus further includes at least one fourth circuit configured to generate the time-varying electric current in response to a received portion of the first time-varying magnetic field.

BACKGROUND Field

The present application relates generally to systems and methods forfacilitating wireless power and data transmission, and morespecifically, for facilitating wireless power and data transmissionbetween an external portion and an implanted portion of an implantedmedical system.

Description of the Related Art

Medical devices have provided a wide range of therapeutic benefits torecipients over recent decades. Medical devices can include internal orimplantable components/devices, external or wearable components/devices,or combinations thereof (e.g., a device having an external componentcommunicating with an implantable component). Medical devices, such astraditional hearing aids, partially or fully-implantable hearingprostheses (e.g., bone conduction devices, mechanical stimulators,cochlear implants, etc.), pacemakers, defibrillators, functionalelectrical stimulation devices, and other medical devices, have beensuccessful in performing lifesaving and/or lifestyle enhancementfunctions and/or recipient monitoring for a number of years.

The types of medical devices and the ranges of functions performedthereby have increased over the years. For example, many medicaldevices, sometimes referred to as “implantable medical devices,” nowoften include one or more instruments, apparatus, sensors, processors,controllers or other functional mechanical or electrical components thatare permanently or temporarily implanted in a recipient. Thesefunctional devices are typically used to diagnose, prevent, monitor,treat, or manage a disease/injury or symptom thereof, or to investigate,replace or modify the anatomy or a physiological process. Many of thesefunctional devices utilize power and/or data received from externaldevices that are part of, or operate in conjunction with, implantablecomponents.

SUMMARY

In one aspect disclosed herein, an apparatus comprises at least onefirst circuit configured to generate a first time-varying magnetic fieldfor magnetic induction power transfer to a device. The apparatus furthercomprises at least one second circuit configured to generate and/orreceive a second time-varying magnetic field for magnetic induction datatransfer to and/or from the device. The apparatus further comprises atleast one third circuit configured to generate a third time-varyingmagnetic field in response to a time-varying electric current, the thirdtime-varying magnetic field configured to at least partially inhibitdegradation of said data transfer from the first time-varying magneticfield. The apparatus further comprises at least one fourth circuitconfigured to generate the time-varying electric current in response toa received portion of the first time-varying magnetic field.

In another aspect disclosed herein, a method comprises transferringpower via a first magnetic induction link in a first region. The methodfurther comprises transferring data via a second magnetic induction linkin a second region, said transferring data simultaneous with saidtransferring power. The method further comprises generating an electriccurrent indicative of a first magnetic field from said first magneticinduction link. The method further comprises, in response to theelectric current, generating a second magnetic field in the secondregion in opposition to at least a portion of the first magnetic fieldwithin the second region.

In another aspect disclosed herein, an apparatus comprises magneticinduction power transfer circuitry configured to generate an inductionpower transfer magnetic field. The apparatus further comprises at leastone circuit that is sensitive to the induction power transfer magneticfield. The apparatus further comprises protection circuitry configuredto generate a protection magnetic field in response to an electriccurrent. The protection magnetic field is configured to at leastpartially protect the at least one circuit from the induction powertransfer magnetic field. The apparatus further comprises circuitryconfigured to generate the electric current in response to the inductionpower transfer magnetic field or in response to a signal indicative ofthe induction power transfer magnetic field.

BRIEF DESCRIPTION OF THE DRAWINGS

Implementations are described herein in conjunction with theaccompanying drawings, in which:

FIG. 1 is a perspective view of an example cochlear implant auditoryprosthesis implanted in a recipient in accordance with certainimplementations described herein;

FIGS. 2A-2G schematically illustrate planar projection views of variousexample apparatus in accordance with certain implementations describedherein;

FIG. 3 schematically illustrates an example apparatus in accordance withcertain implementations described herein;

FIG. 4A schematically illustrates a calculation of the firsttime-varying magnetic field generated by the power transfer coil withouteither the cancellation coil or the pick-up coil.

FIG. 4B schematically illustrates a calculation of the superposition ofthe first time-varying magnetic field generated by the power transfercoil and the third time-varying magnetic field with both thecancellation coil and the pick-up coil in accordance with certainimplementations described herein;

FIG. 5 is a flow diagram of an example method in accordance with certainimplementations described herein; and

FIGS. 6A-6B schematically illustrate two example apparatus configured toreduce degradation of various types of low-power systems that aresensitive to magnetic fields in accordance with certain implementationsdescribed herein.

DETAILED DESCRIPTION

In certain systems, magnetic induction power transfer is performedconcurrently and in close proximity to other low-power operations whichcan experience degradation due to the large time-varying magnetic fieldsinvolved in the magnetic induction power transfer. For example, anexternal portion of an auditory prosthesis can utilize magneticinduction to provide power transcutaneously to an implanted portion ofthe auditory prosthesis while also using magnetic induction tocommunicate data transcutaneously with the implanted portion. Due to therelatively small size of the external portion (e.g., an over-the-ear orbutton sound processor), the low-power magnetic induction data transferlink can experience excessive noise and other interference due to theconcurrent operation of the nearby high-power magnetic induction powertransfer link. For another example, signals from an electromagneticmicrophone of the external portion of the auditory prosthesis can bedisrupted by the concurrent operation of the nearby high-power magneticinduction power transfer link to the implanted portion.

Certain implementations described herein comprise cancellation circuitryconfigured to generate a magnetic field configured to destructivelyinterfere with (e.g., counteract; in opposition to) the portion of thelarge time-varying magnetic field in the region of the circuitryperforming the low-power operation, thereby at least partiallyinhibiting the degradation of the low-power operation. In certainimplementations, the cancellation circuitry is powered by magneticinduction from at least one pick-up coil receiving a portion of thelarge time-varying magnetic field (e.g., passively powered). In certainother implementations, the cancellation circuitry is powered by aseparate power supply in response to a sensor signal indicative of thelarge time-varying magnetic field (e.g., actively powered).

The teachings detailed herein are applicable, in at least someimplementations, to any type of implantable medical device (e g ,implantable sensory prostheses) comprising a first portion (e.g.,external to a recipient) and a second portion (e.g., implanted on orwithin the recipient), the first portion configured to wirelesslytransmit power to the second portion and to wirelessly communicate withthe second portion. For example, the implantable medical device cancomprise an auditory prosthesis system utilizing an external soundprocessor configured to transcutaneously provide power and data (e.g.,control signals) to an implanted assembly (e.g., comprising an actuator)that generates stimulation signals that are perceived by the recipientas sounds. Examples of auditory prosthesis systems compatible withcertain implementations described herein include but are not limited to:electro-acoustic electrical/acoustic systems, cochlear implant devices,implantable hearing aid devices, middle ear implant devices, DirectAcoustic Cochlear Implant (DACI), middle ear transducer (MET),electro-acoustic implant devices, other types of auditory prosthesisdevices, and/or combinations or variations thereof, or any othersuitable hearing prosthesis system with or without one or more externalcomponents Implementations can include any type of medical device thatcan utilize the teachings detailed herein and/or variations thereof.

Merely for ease of description, apparatus and methods disclosed hereinare primarily described with reference to an illustrative medicaldevice, namely a cochlear implant. However, the teachings detailedherein and/or variations thereof may also be used with a variety ofother medical devices that provide a wide range of therapeutic benefitsto recipients, patients, or other users. In some implementations, theteachings detailed herein and/or variations thereof can be utilized inother types of implantable medical devices beyond auditory prostheses.For example, apparatus and methods disclosed herein and/or variationsthereof may also be used with one or more of the following: vestibulardevices (e.g., vestibular implants); visual devices (e.g., bionic eyes);visual prostheses (e.g., retinal implants); sensors; cardiac pacemakers;drug delivery systems; defibrillators; functional electrical stimulationdevices; catheters; brain implants; seizure devices (e.g., devices formonitoring and/or treating epileptic events); sleep apnea devices;electroporation; etc. The concepts described herein and/or variationsthereof can be applied to any of a variety of implantable medicaldevices comprising an implanted component configured to use magneticinduction to communicate transcutaneously with an external component(e.g., receive control signals from the external component and/ortransmit sensor signals to the external component) while using magneticinduction to receive power from the external component. In still otherimplementations, the teachings detailed herein and/or variations thereofcan be utilized in other types of systems beyond medical devicesutilizing magnetic induction for both wireless power transfer and datacommunication. For example, such other systems can include one or moreof the following: consumer products (e.g., smartphones; IoT devices) andelectric vehicles (e.g., automobiles).

FIG. 1 is a perspective view of an example cochlear implant auditoryprosthesis 100 implanted in a recipient in accordance with certainimplementations described herein. The example auditory prosthesis 100 isshown in FIG. 1 as comprising an implanted stimulator unit 120 (e.g., anactuator) and an external microphone assembly 124 (e.g., a partiallyimplantable cochlear implant). An example auditory prosthesis 100 (e.g.,a totally implantable cochlear implant) in accordance with certainimplementations described herein can replace the external microphoneassembly 124 shown in FIG. 1 with a subcutaneously implantable assemblycomprising an acoustic transducer (e.g., microphone), as described morefully herein.

As shown in FIG. 1 , the recipient normally has an outer ear 101, amiddle ear 105, and an inner ear 107. In a fully functional ear, theouter ear 101 comprises an auricle 110 and an ear canal 102. An acousticpressure or sound wave 103 is collected by the auricle 110 and ischanneled into and through the ear canal 102. Disposed across the distalend of the ear canal 102 is a tympanic membrane 104 which vibrates inresponse to the sound wave 103. This vibration is coupled to oval windowor fenestra ovalis 112 through three bones of middle ear 105,collectively referred to as the ossicles 106 and comprising the malleus108, the incus 109, and the stapes 111. The bones 108, 109, and 111 ofthe middle ear 105 serve to filter and amplify the sound wave 103,causing the oval window 112 to articulate, or vibrate in response tovibration of the tympanic membrane 104. This vibration sets up waves offluid motion of the perilymph within the cochlea 140. Such fluid motion,in turn, activates tiny hair cells (not shown) inside the cochlea 140.Activation of the hair cells causes appropriate nerve impulses to begenerated and transferred through the spiral ganglion cells (not shown)and auditory nerve 114 to the brain (also not shown) where they areperceived as sound.

As shown in FIG. 1 , the example auditory prosthesis 100 comprises oneor more components which are temporarily or permanently implanted in therecipient. The example auditory prosthesis 100 is shown in FIG. 1 withan external component 142 which is directly or indirectly attached tothe recipient's body, and an internal component 144 which is temporarilyor permanently implanted in the recipient (e.g., positioned in a recessof the temporal bone adjacent auricle 110 of the recipient). Theexternal component 142 typically comprises one or more inputelements/devices for receiving input signals at a sound processing unit126. The one or more input elements/devices can include one or moresound input elements (e.g., one or more external microphones 124) fordetecting sound and/or one or more auxiliary input devices (not shown inFIG. 1 ) (e.g., audio ports, such as a Direct Audio Input (DAI); dataports, such as a Universal Serial Bus (USB) port; cable ports, etc.). Inthe example of FIG. 1 , the sound processing unit 126 is abehind-the-ear (BTE) sound processing unit configured to be attached to,and worn adjacent to, the recipient's ear. However, in certain otherimplementations, the sound processing unit 126 has other arrangements,such as by an OTE processing unit (e.g., a component having a generallycylindrical shape and which is configured to be magnetically coupled tothe recipient's head), a mini or micro-BTE unit, an in-the-canal unitthat is configured to be located in the recipient's ear canal, abody-worn sound processing unit, etc.

The sound processing unit 126 of certain implementations includes apower source (not shown in FIG. 1 ) (e.g., battery), a processing module(not shown in FIG. 1 ) (e.g., comprising one or more digital signalprocessors (DSPs), one or more microcontroller cores, one or moreapplication-specific integrated circuits (ASICs), firmware, software,etc. arranged to perform signal processing operations), and an externaltransmitter unit 128. In the illustrative implementation of FIG. 1 , theexternal transmitter unit 128 comprises circuitry that includes at leastone external inductive communication coil 130 (e.g., a wire antenna coilcomprising multiple turns of electrically insulated single-strand ormulti-strand platinum or gold wire). The external transmitter unit 128also generally comprises a magnet (not shown in FIG. 1 ) secureddirectly or indirectly to the at least one external inductivecommunication coil 130. The at least one external inductivecommunication coil 130 of the external transmitter unit 128 is part ofan inductive radio frequency (RF) communication link with the internalcomponent 144. The sound processing unit 126 processes the signals fromthe input elements/devices (e.g., microphone 124 that is positionedexternally to the recipient's body, in the depicted implementation ofFIG. 1 , by the recipient's auricle 110). The sound processing unit 126generates encoded signals, sometimes referred to herein as encoded datasignals, which are provided to the external transmitter unit 128 (e.g.,via a cable). As will be appreciated, the sound processing unit 126 canutilize digital processing techniques to provide frequency shaping,amplification, compression, and other signal conditioning, includingconditioning based on recipient-specific fitting parameters.

The power source of the external component 142 is configured to providepower to the auditory prosthesis 100, where the auditory prosthesis 100includes a battery (e.g., located in the internal component 144, ordisposed in a separate implanted location) that is recharged by thepower provided from the external component 142 (e.g., via atranscutaneous energy transfer link). The transcutaneous energy transferlink is used to transfer power and/or data to the internal component 144of the auditory prosthesis 100. Various types of energy transfer, suchas infrared (IR), electromagnetic, capacitive, and inductive transfer,may be used to transfer the power and/or data from the externalcomponent 142 to the internal component 144. During operation of theauditory prosthesis 100, the power stored by the rechargeable battery isdistributed to the various other implanted components as needed.

The internal component 144 comprises an internal receiver unit 132, astimulator unit 120, and an elongate stimulation assembly 118. In someimplementations, the internal receiver unit 132 and the stimulator unit120 are hermetically sealed within a biocompatible housing, sometimescollectively referred to as a stimulator/receiver unit. The internalreceiver unit 132 comprises at least one internal inductivecommunication coil 136 (e.g., a wire antenna coil comprising multipleturns of electrically insulated single-strand or multi-strand platinumor gold wire), and generally, a magnet (not shown in FIG. 1 ) fixedrelative to the at least one internal inductive communication coil 136.The at least one internal inductive communication coil 136 receivespower and/or data signals from the at least one external inductivecommunication coil 130 via a transcutaneous energy transfer link (e.g.,an inductive RF link). The stimulator unit 120 generates stimulationsignals (e.g., electrical stimulation signals; optical stimulationsignals) based on the data signals, and the stimulation signals aredelivered to the recipient via the elongate stimulation assembly 118.

The elongate stimulation assembly 118 has a proximal end connected tothe stimulator unit 120, and a distal end implanted in the cochlea 140.The stimulation assembly 118 extends from the stimulator unit 120 to thecochlea 140 through the mastoid bone 119. In some embodiments, thestimulation assembly 118 can be implanted at least in the basal region116, and sometimes further. For example, the stimulation assembly 118can extend towards an apical end of the cochlea 140, referred to as thecochlea apex 134. In certain circumstances, the stimulation assembly 118can be inserted into the cochlea 140 via a cochleostomy 122. In othercircumstances, a cochleostomy can be formed through the round window121, the oval window 112, the promontory 123, or through an apical turn147 of the cochlea 140.

The elongate stimulation assembly 118 comprises a longitudinally alignedand distally extending array 146 (e.g., electrode array; contact array)of stimulation elements 148 (e.g., electrical electrodes; electricalcontacts; optical emitters; optical contacts). The stimulation elements148 are longitudinally spaced from one another along a length of theelongate body of the stimulation assembly 118. For example, thestimulation assembly 118 can comprise an array 146 comprising twenty-two(22) stimulation elements 148 that are configured to deliver stimulationto the cochlea 140. Although the array 146 of stimulation elements 148can be disposed on the stimulation assembly 118, in most practicalapplications, the array 146 is integrated into the stimulation assembly118 (e.g., the stimulation elements 148 of the array 146 are disposed inthe stimulation assembly 118). As noted, the stimulator unit 120generates stimulation signals (e.g., electrical signals; opticalsignals) which are applied by the stimulation elements 148 to thecochlea 140, thereby stimulating the auditory nerve 114.

While FIG. 1 schematically illustrates an auditory prosthesis 100utilizing an external component 142 comprising an external microphone124, an external sound processing unit 126, and an external powersource, in certain other implementations, one or more of the microphone124, sound processing unit 126, and power source are implantable on orwithin the recipient (e.g., within the internal component 144). Forexample, the auditory prosthesis 100 can have each of the microphone124, sound processing unit 126, and power source implantable on orwithin the recipient (e.g., encapsulated within a biocompatible assemblylocated subcutaneously), and can be referred to as a totally implantablecochlear implant (“TICI”). For another example, the auditory prosthesis100 can have most components of the cochlear implant (e.g., excludingthe microphone, which can be an in-the-ear-canal microphone) implantableon or within the recipient, and can be referred to as a mostlyimplantable cochlear implant (“MICI”).

FIGS. 2A-2G schematically illustrate planar projection views of variousexample apparatus 200 in accordance with certain implementationsdescribed herein. The apparatus 200 comprises at least one first circuit210 configured to generate a first time-varying magnetic field 212 formagnetic induction power transfer to a device. The apparatus 200 furthercomprises at least one second circuit 220 configured to generate and/orreceive a second time-varying magnetic field (not shown) for magneticinduction data transfer to and/or from the device. The apparatus 200further comprises at least one third circuit 230 configured to generatea third time-varying magnetic field 232 in response to a time-varyingelectric current 242. The third time-varying magnetic field 232 isconfigured to at least partially inhibit degradation of said datatransfer from the first time-varying magnetic field 212. The apparatus200 further comprises at least one fourth circuit 240 configured togenerate the time-varying electric current 242 in response to a receivedportion of the first time-varying magnetic field 212 or in response to asignal indicative of the first time-varying magnetic field 212.

In certain implementations, the apparatus 200 is an external portion ofa medical system (e.g., a portion of the medical system that is notimplanted on or within the recipient) and the device comprises animplanted portion of the medical system (e.g., a portion implanted on orwithin a recipient). For example, the apparatus 200 can comprise anexternal portion (e.g., a sound processing unit 126) of an auditoryprosthesis 100 (e.g., a cochlear implant system). As schematicallyillustrated by FIGS. 2A-2G, the apparatus 200 of certain implementationscomprises a housing 250 (e.g., polymer; plastic) configured to be wornexternally by the recipient and containing the at least one firstcircuit 210, the at least one second circuit 220, the at least one thirdcircuit 230, and the at least one fourth circuit 240. The housing 250 ofcertain implementations is configured to further contain at least onepower source (e.g., battery) and processing circuitry configured toreceive and process data signals to be communicated to the implantedportion of the medical device via the at least one second circuit 220.For example, for an auditory prosthesis 100, the processing circuitrycan be configured to process data signals received from a microphone 124and to generate encoded data signals (e.g., utilizing digital processingtechniques for frequency shaping, amplification, compression, and/orother signal conditioning, including conditioning based onrecipient-specific fitting parameters) which are provided to theimplanted portion of the auditory prosthesis 100 via the at least onesecond circuit 220.

The housing 250 of certain implementations is configured to be held inplace externally to the recipient during power transfer (e.g., using theat least one first circuit 210) and data transfer (e.g., using the atleast one second circuit 220). For example, as schematically illustratedby FIG. 2A, the apparatus 200 can further comprise at least one magnet260 (e.g., within the housing 250). The at least one magnet 260 can beconfigured to create an attractive magnetic force with a correspondingmagnetic material (e.g., a magnet) of the implanted portion of themedical system, the attractive magnetic force configured to hold theapparatus 200 in an operative position relative to the implantedportion. When the apparatus 200 is in the operative position, the atleast one first circuit 210 forms a magnetic inductive RF power transferlink (e.g., for transcutaneous power transfer) with correspondingcircuitry of the implanted portion, and the at least one second circuit220 forms a magnetic inductive RF data transfer link (e.g., fortranscutaneous data transfer) with corresponding circuitry of theimplanted portion.

In certain implementations, the at least one first circuit 210 comprisesat least one electrically conductive power transfer coil 214 configuredto be operationally coupled by magnetic induction to the correspondingcircuitry (e.g., at least one electrically conductive power transfercoil) of the implanted portion. For example, the power transfer coil 214can comprise an electrically conductive conduit (e.g., wire; conductivetrace on a printed circuit board). The at least one power transfer coil214 is configured to receive a time-varying electric current (e.g., fromcontroller circuitry of the apparatus 200) and to generate the firsttime-varying magnetic field 212 (e.g., an inductive power transfermagnetic field) that transfers power via magnetic induction to thecorresponding circuitry of the implanted portion. In certainimplementations, the first time-varying (e.g., alternating) magneticfield 212 has a frequency in a range of 100 kHz to 100 MHz (e.g., 5 MHz;6.78 MHz; 12 MHz; 49 MHz). In certain implementations in which theapparatus 200 comprises an external portion of a medical system, thepower transfer is in a range of 1 mW to 500 mW. In certain otherimplementations, the power transfer in a range of 1 W to 1 kW (e.g., forconsumer devices; for IoT devices) or in a range of 1 kW to 100 kW(e.g., for vehicles).

In certain implementations, the power transfer coil 214 of the at leastone first circuit 210 has one or more (e.g., 2, 3, 4, 5, or more)windings, a generally planar, generally circular shape (e.g., having aninner diameter in a range of 10 mm to 50 mm), and bounds a region havingan area in a range of 70 mm² to 850 mm². Other shapes (e.g., non-planar;elliptical; square; rectangular; polygonal; geometric; irregular;symmetric; non-symmetric) and sizes of the power transfer coil 214 arealso compatible with certain implementations described herein. FIG. 2Ashows the power transfer coil 214 encircling the magnet 260 (e.g., themagnet 260 and the power transfer coil 214 are substantially concentricand/or substantially planar with one another; the magnet 260 having aprojection in a projection plane that is within a projection of thepower transfer coil 214 in the projection plane). In certain otherimplementations, the power transfer coil 214 is positioned at otherpositions (e.g., alongside; non-concentric) relative to the magnet 260.

In certain implementations, the at least one second circuit 220comprises at least one antenna 224 configured to be operationallycoupled by magnetic induction to the corresponding circuitry (e.g., atleast one antenna) of the implanted portion. The at least one antenna224 is configured to transmit data to the corresponding circuitry viathe second time-varying magnetic field (e.g., by generating adata-encoded time-varying magnetic field in response to a data-encodedtime-varying electric signal from controller circuitry of the apparatus200) and/or to receive data from the corresponding circuitry via thesecond time-varying magnetic field (e.g., by receiving a data-encodedtime-varying magnetic field from the corresponding circuitry andgenerating a data-encoded time-varying electric signal that is providedto the controller circuitry of the apparatus 200). For example, the atleast one antenna 224 can comprise an electrically conductive conduit(e.g., a conductive coil having an axis and wound around a ferrite rodhaving a length that is in a range of 4 mm to 10 mm and a diameter in arange of 1.5 mm to 3 mm; a conductive coil having an axis and woundaround an air-filled region). In certain implementations, thedata-encoded time-varying (e.g., alternating) magnetic field generatedor received by the at least one second circuit 220 has a frequency(e.g., in a range of 10 MHz to 20 MHz) and the power of the datatransfer is orders of magnitude less than the power transferred by theat least one first circuit 210 (e.g., the power of the data transfer ison the order of nW or μW).

In certain implementations, the at least one third circuit 230 comprisesat least one cancellation coil 234 in proximity to the at least oneantenna 224 of the at least one second circuit 220 (e.g., thecancellation coil 234 bounds a region containing the antenna 224). Forexample, the cancellation coil 234 can comprise an electricallyconductive conduit (e.g., wire; conductive trace on a printed circuitboard). As schematically illustrated by FIG. 2A, the cancellation coil234 can encircle the antenna 224 (e.g., the antenna 224 and thecancellation coil 234 are substantially concentric and/or substantiallyplanar with one another; the antenna 224 has a projection in aprojection plane that is within a projection of the cancellation coil234 in the projection plane) and each of the antenna 224 and thecancellation coil 234 are outside a region bounded by the power transfercoil 214 (e.g., each of the antenna 224 and the cancellation coil 234has a projection in a projection plane that is outside a projection ofthe power transfer coil 214 in the projection plane). In certainimplementations, the cancellation coil 234 has one or more (e.g., 2, 3,4, 5, or more) windings, a generally planar, generally circular shape(e.g., having an inner diameter in a range of 2 mm to 20 mm), and boundsa region having an area in a range of 3 mm² to 300 mm². Other shapes(e.g., non-planar; elliptical; square; rectangular; polygonal;geometric; irregular; symmetric; non-symmetric) and sizes of thecancellation coil 234 are also compatible with certain implementationsdescribed herein. In certain implementations in which the antenna 224comprises a conductive coil having an axis and wound around either aferrite rod or an air-filled region, the antenna 224 can be positionedwith the axis of the antenna 224 perpendicular to an axis of thecancellation coil 234 (e.g., the axis of the antenna 224 parallel to aprinted circuit board on which the cancellation coil 234 is formed).

In certain implementations, the at least one cancellation coil 234 isconfigured to generate the third time-varying magnetic field 232 (e.g.,a protection magnetic field) in response to a time-varying electriccurrent 242 received by the at least one cancellation circuit 234 fromthe at least one fourth circuit 240. The third time-varying magneticfield 232 is configured to at least partially inhibit (e.g., reduce;cancel; prevent; avoid; minimize) degradation of the data transferbetween the at least one second circuit 220 and the correspondingcircuitry of the implanted portion, the degradation due to the firsttime-varying magnetic field 212 from the at least one first circuit 210.For example, the third time-varying magnetic field 232 is configured tobe in opposition to (e.g., to be in opposite phase with) at least aportion of the first time-varying magnetic field 212 such that the thirdtime-varying magnetic field 232 destructively interferes with at leastthe portion of the first time-varying magnetic field 212 within theregion bounded by the at least one cancellation coil 234 (e.g., at theat least one antenna 224 of the at least one second circuit 220).

In certain implementations, the destructive interference of the firsttime-varying magnetic field 212 within the region by the thirdtime-varying magnetic field 232 at least partially reduces (e.g.,counteracts; opposes; cancels; minimizes) a magnitude of thesuperposition of the first and third time-varying magnetic fields 212,232 (e.g., net magnetic field) within the region bounded by the at leastone cancellation coil 234. For example, the third time-varying magneticfield 232 can have a substantially opposite phase to that of the firsttime-varying magnetic field 212 and can have a magnitude at the antenna224 that is substantially equal to the magnitude of the firsttime-varying magnetic field 212 at the antenna 224 (e.g., substantiallytotal destructive interference at the antenna 224; complete cancellationat the antenna 224; substantially zero net magnetic field). In certainimplementations, the third time-varying magnetic field 232 at theantenna 224 has a magnitude in at least one direction (e.g.,substantially perpendicular to the plane of the cancellation coil 234)that is substantially equal and opposite to the magnitude of the firsttime-varying magnetic field 212 at the antenna 224 in the at least onedirection (e.g., such that the net magnetic field from the superpositionof the first and third time-varying magnetic fields 212, 232 in thedirection substantially perpendicular to the plane of the cancellationcoil 234 is substantially zero).

In certain implementations, examples of which are schematicallyillustrated in FIGS. 2A-2F, the at least one fourth circuit 240comprises at least one pick-up coil 244 in series electricalcommunication with the at least one third circuit 230. For example, theat least one pick-up coil 244 can comprise an electrically conductiveconduit (e.g., wire; conductive trace on a printed circuit board). Asschematically illustrated by FIGS. 2A-2F, the at least one pick-up coil244 can be in series electrical communication with the cancellation coil234 of the at least one third circuit 230. The at least one pick-up coil244 is configured to generate (e.g., passively) the time-varyingelectric current 242 via magnetic induction resulting from the receivedportion of the first time-varying magnetic field 212 and to provide thetime-varying electric current 242 to the cancellation coil 234. Forexample, the at least one pick-up coil 244 can be spaced away from thecancellation coil 234 and in electrical communication with thecancellation coil 234 via electrically conductive conduits (e.g., wires;conductive traces on a printed circuit board).

In certain implementations, the pick-up coil 244 has one or more (e.g.,2, 3, 4, 5, or more) windings, a generally planar, generally circularshape (e.g., having an inner diameter in a range of 2 mm to 50 mm), andbounds a region having an area in a range of 3 mm² to 850 mm². Othershapes (e.g., non-planar; elliptical; square; rectangular; polygonal;geometric; irregular; symmetric; non-symmetric) and sizes of the pick-upcoil 244 are also compatible with certain implementations describedherein.

As described by Lenz's law, a changing magnetic field will inducecurrents to flow within a conductor exposed to the changing magneticfield, the currents generating secondary magnetic fields that oppose thechanging magnetic field. Therefore, a cancellation coil 234 exposed tothe first time-varying magnetic field 212 will generate magnetic fieldsthat oppose the first time-varying magnetic field 212 within thecancellation coil 234. However, due to the resistance and imperfectionsof the cancellation coil 234, this opposition is only partial and thefirst time-varying magnetic field 212 is only partially canceled by thesecondary magnetic fields generated by the induced currents in thecancellation coil 234.

In certain implementations, the at least one pick-up coil 244 isconfigured to generate and provide sufficient electric current to thecancellation coil 234 such that the cancellation coil 234 generates thethird time-varying magnetic field 232 with sufficient magnitude toproduce a predetermined reduction of a magnitude of the superposition ofthe first and third time-varying magnetic fields 212, 232 within theregion bounded by the cancellation coil 234. In certain suchimplementations, the characteristics of the at least one cancellationcoil 234 and/or the at least one pick-up coil 244 are selected such thatthe at least one cancellation coil 234 generates the third time-varyingmagnetic field 232 in response to the electric current from the at leastone pick-up coil 244 (e.g., the electric current magnetically induced inthe at least one pick-up coil 244 by the first time-varying magneticfield 212 is greater than the electric current magnetically induced inthe cancellation coil 234 by the first time-varying magnetic field 212).Examples of such characteristics include but are not limited to one ormore of the following: the relative positions of the cancellation coil234 and the pick-up coil 244 relative to the power transfer coil 212(e.g., which determine the magnitudes of the time-varying magnetic field212 at the cancellation coil 234 and at the pick-up coil 244); the sizes(e.g., areas) of the cancellation coil 234 and/or the pick-up coil 244;and the number of windings of the cancellation coil 234 and/or thepick-up coil 244. Various example implementations are schematicallyshown in FIGS. 2A-2F, which are described below in reference to theequations (e.g., for planar coils) for magnetic flux:Φ(t)=ΦB(t)dA≅NAB(t) and magnetically induced current:

${{I(t)} = {\frac{1}{R}\frac{d{\Phi(t)}}{dt}}},$

where Φ(t) is the time-varying magnetic flux flowing through the area ofthe coil, B(t) is the time-varying magnetic field at the coil, R is theresistance of the coil, N is the number of windings of the coil, and Ais the area of the coil.

For example, as schematically illustrated by FIG. 2A, the pick-up coil244 is outside a region encircled by the at least one power transfercoil 214 (e.g., the pick-up coil 244 has a projection in a projectionplane that is outside a projection of the power transfer coil 214 in theprojection plane), and the pick-up coil 244 and the cancellation coil234 have substantially equal areas (e.g., substantially equal shapes andsizes) and numbers of windings, and the pick-up coil 244 is positionedcloser to the power transfer coil 214 than is the cancellation coil 234(e.g., a distance between the centers of the pick-up coil 244 and thepower transfer coil 214 is less than a distance between the centers ofthe cancellation coil 234 and the power transfer coil 214). Because thepick-up coil 244 is closer to the power transfer coil 214, the magnitudeof the portion of the first time-varying magnetic field 212 B(t) flowingthrough the area A of the pick-up coil 244 is greater than the magnitudeof the portion of the first time-varying magnetic field 212 B(t) flowingthrough the area A of the cancellation coil 234, such that thecumulative electric current I(t) flowing through the cancellation coil234 generates the third time-varying magnetic field 232.

For another example, as schematically illustrated by FIG. 2B, thepick-up coil 244 is outside a region encircled by the at least one powertransfer coil 214 (e.g., the pick-up coil 244 has a projection in aprojection plane that is outside a projection of the power transfer coil214 in the projection plane), and the pick-up coil 244 is positioned ata substantially equal distance from the power transfer coil 214 as isthe cancellation coil 234 (e.g., the distance between the centers of thepick-up coil 244 and the power transfer coil 214 is substantially equalto the distance between the centers of the cancellation coil 234 and thepower transfer coil 214), but the pick-up coil 244 has a larger area Aand/or a larger number of windings N than does the cancellation coil234.

For another example, as schematically illustrated by FIG. 2C, thepick-up coil 244 is within a region encircled by the at least one powertransfer coil 214 (e.g., the pick-up coil 244 and the power transfercoil 214 are substantially concentric and/or substantially planar withone another; the pick-up coil 244 has a projection in a projection planethat is within a projection of the power transfer coil 214 in theprojection plane). Because the pick-up coil 244 is within the inner areaof the power transfer coil 214, the magnitude of the time-varyingmagnetic flux from the portion of the first time-varying magnetic field212 flowing through the area of the pick-up coil 244 is greater than themagnitude of the time-varying magnetic flux from the portion of thefirst time-varying magnetic field 212 flowing through the area of thecancellation coil 234, such that the electric current flowing throughthe cancellation coil 234 generates the third time-varying magneticfield 232.

For another example, as schematically illustrated by FIG. 2D, the atleast one pick-up coil 244 comprises a plurality of pick-up coils 244 inseries electrical communication with the cancellation coil 234, spacedaway from the cancellation coil 234 and one another, and outside aregion encircled by the at least one power transfer coil 214 (e.g., thepick-up coils 244 have projections in a projection plane that areoutside a projection of the power transfer coil 214 in the projectionplane). Because the cumulative areas A of the pick-up coils 244 isgreater than the area A of the cancellation coil 234, the magnitude ofthe time-varying magnetic flux from the portion of the firsttime-varying magnetic field 212 flowing through the cumulative areas ofthe pick-up coil 244 is greater than the magnitude of the time-varyingmagnetic flux from the portion of the first time-varying magnetic field212 flowing through the area of the cancellation coil 234, such that theelectric current flowing through the cancellation coil 234 generates thethird time-varying magnetic field 232.

For another example, as schematically illustrated by FIG. 2E, thepick-up coil 244 is outside a region encircled by the at least one powertransfer coil 214 (e.g., the pick-up coil 244 has a projection in aprojection plane that is outside a projection of the power transfer coil214 in the projection plane), is closer to the at least one powertransfer coil 214 than is the cancellation coil 234, and has a largerarea and/or a larger number of windings than does the cancellation coil234.

For another example, as schematically illustrated by FIG. 2F, the atleast one pick-up coil 244 comprises a pair of pick-up coils 244 a, 244b in series electrical communication with one another and with thecancellation coil 234. A first pick-up coil 244 a is outside a regionencircled by the at least one power transfer coil 214 (e.g., the firstpick-up coil 244 a has a projection in a projection plane that isoutside a projection of the power transfer coil 214 in the projectionplane) and a second pick-up coil 244 b is inside the region encircled bythe at least one power transfer coil 214 (e.g., the second pick-up coil244 b has a projection in a projection plane that is inside a projectionof the power transfer coil 214 in the projection plane). In certainimplementations, the area of the first pick-up coil 244 a and the areaof the second pick-up coil 244 b are substantially equal to one anotherand/or the number of windings of the first pick-up coil 244 a and thenumber of windings of the second pick-up coil 244 b are substantiallyequal to one another. The direction of the magnetic field within thefirst pick-up coil 244 a is substantially opposite to the direction ofthe magnetic field within the second pick-up coil 244 b since the firstpick-up coil 244 a is within the region encircled by the power transfercoil 214 and the second pick-up coil 244 b is outside the regionencircled by the power transfer coil 214. The first pick-up coil 244 aand the second pick-up coil 244 b have a cross-over portion therebetweento compensate for these different directions of the magnetic fields,such that the electrical current induced in one of the first and secondpick-up coils 244 a, 244 b is in the clockwise direction and theelectrical current induced in the other of the first and second pick-upcoils 244 a, 244 b is in the counterclockwise direction (e.g., the twoelectrical currents do not oppose one another when provided to thecancellation coil 234).

FIG. 3 schematically illustrates an example apparatus 200 in accordancewith certain implementations described herein. The apparatus 200 of FIG.3 comprises a first circuit 210 comprising a power transfer coil 214, asecond circuit 220 comprising an antenna 224, a third circuit 230comprising a cancellation coil 234, and a fourth circuit 240 comprisinga pick-up coil 244. The power transfer coil 214 of FIG. 3 encircles themagnet 260, and the pick-up coil 244 of FIG. 3 comprises multiplewindings while the cancellation coil 234 comprises a single winding. Inaddition, each of the power transfer coil 214, the cancellation coil234, and the pick-up coil 244 is substantially planar and aresubstantially planar with one another (e.g., each of the coils 214, 234,244 are substantially in the X-Y plane). In certain otherimplementations, two or more of the power transfer coil 214, thecancellation coil 234, and the pick-up coil 244 are not substantiallyplanar with one another and/or are not substantially planar with oneanother (e.g., are spaced above or below the X-Y plane).

FIG. 4A schematically illustrates a calculation of the firsttime-varying magnetic field 212 generated by the power transfer coil 214without either the cancellation coil 234 or the pick-up coil 244. Thelines generally encircling the power transfer coil 214 representdifferent magnitudes of the first time-varying magnetic field 212 alongthe Z direction (perpendicular to the X-Y plane) generated by the powertransfer coil 214 in the X-Y plane. FIG. 4B schematically illustrates acalculation of the superposition of the first time-varying magneticfield 212 generated by the power transfer coil 214 and the thirdtime-varying magnetic field 232 with both the cancellation coil 234 andthe pick-up coil 244 in accordance with certain implementationsdescribed herein. A comparison of FIGS. 4A and 4B illustrates that themagnitudes along the Z direction of the superposition of the firsttime-varying magnetic field 212 and the third time-varying magneticfield 232 in the region of the antenna 224 within the area bounded bythe cancellation coil 234 is reduced by the cancellation coil 234 andthe pick-up coil 244.

In certain implementation, an example of which is schematicallyillustrated in FIG. 2E, the at least one fourth circuit 240 comprises atleast one sensor 246 and control circuitry 248 (e.g., a microprocessor;an application-specific integrated circuit; an amplifier) in serieselectrical communication with the at least one third circuit 230 (e.g.,the cancellation coil 234). The at least one sensor 246 can comprise asensor coil comprising an electrically conductive conduit (e.g., wire;conductive trace on a printed circuit board), the sensor coil configuredto generate (e.g., passively) a sensor signal via magnetic inductionresulting from the received portion of the first time-varying magneticfield 212. The sensor signal is generated in response to the firsttime-varying magnetic field 212 at the at least one sensor 246, and isindicative of the first time-varying magnetic field 212. The controlcircuitry 248 is configured to respond to the sensor signal bygenerating (e.g., actively) the time-varying electric current 242, whichis indicative of the first time-varying magnetic field 212 at the atleast one second circuit 220. In certain implementations, the controlcircuitry 248 is configured to receive electrical power from the samepower source of the apparatus 200 that powers the at least one firstcircuit 210, while in certain other implementations, the controlcircuitry 248 further comprise a separate power source (e.g., a battery)from which the control circuitry 248 receives electrical power. Forexample, the control circuitry 248 can determine, in response to thesensor signal, an appropriate magnitude and/or phase of the time-varyingelectric current 242 to be provided to the cancellation coil 234 suchthat the resultant third time-varying magnetic field 232 at the antenna224 destructively interferes with the first time-varying magnetic field212 at the antenna 224. In certain implementations, the at least onesensor 246 is positioned at or near the antenna 224 such that the sensorsignal is indicative of the first time-varying magnetic field 212 at ornear the antenna 224, and the control circuitry 248 is configured to usethe sensor signal as a feedback signal to optimize (e.g., “zero out”)the first time-varying magnetic field 212 at or near the antenna 224while the first time-varying magnetic field 212 elsewhere is configuredto provide the desired amount of power transfer.

In certain implementations, the at least one fourth circuit 240comprises at least a portion of the at least one first circuit 210. Forexample, instead of the at least one sensor 246 of FIG. 2G, at least aportion of the at least one first circuit 210 can be configured togenerate a signal indicative of the first time-varying magnetic field212 and to provide the signal to the control circuitry 248 of the fourthcircuit 240. The control circuitry 248 can be configured to respond tothe signal by generating (e.g., actively) the time-varying electriccurrent 242. In certain such implementations, the third time-varyingmagnetic field 232 and the first time-varying magnetic field 212 havethe same frequency content (e.g., the same phase and the same shape) asone another. The magnitude of the third time-varying magnetic field 232can be adjusted (e.g., optimized) by controlling (e.g., limiting) thetime-varying electric current 242 provided to the at least one thirdcircuit 230 (e.g., by controlling the gain of an amplifier; by using aseries resistance; etc.).

FIG. 5 is a flow diagram of an example method 500 in accordance withcertain implementations described herein. In an operational block 510,the method 500 comprises transferring power via a first magneticinduction link in a first region. For example, the first magneticinduction link can utilize the at least one first circuit 210 (e.g.,energizing the first magnetic induction link by transmitting electriccurrent along the power transfer coil 214 to transfer power via magneticinduction to a corresponding circuit).

In an operational block 520, the method 500 further comprisestransferring data via a second magnetic induction link in a secondregion, the data transfer simultaneous with the power transfer. Forexample, the second magnetic induction link can energize the at leastone second circuit 220 (e.g., transmitting electric current along theantenna 224) at the same time that the first magnetic induction link isenergized. In certain implementations, the second region is within thefirst region (e.g., the power transfer coil 214 encircles the antenna224), while in certain other implementations, the second region isseparate from the first region (e.g., the power transfer coil 214 doesnot encircle the antenna 224; the antenna 224 is alongside the powertransfer coil 214).

In an operational block 530, the method 500 further comprises generatingan electric current indicative of a first magnetic field from the firstmagnetic induction link. In certain implementations, the electriccurrent is generated by the at least one fourth circuit 240. Forexample, the electric current can be magnetically induced in the pick-upcoil 244 (e.g., using the first magnetic field to magnetically inducethe electric current in the pick-up coil 244). For another example, theelectric current can be generated by magnetically inducing a sensorsignal (e.g., using a sensor coil 246) indicative of the first magneticfield and using circuitry (e.g., control circuitry 248) to generate theelectric current in response to the sensor signal.

In an operational block 540, the method 500 further comprisesgenerating, in response to the electric current, a second magnetic fieldin the second region in opposition to at least a portion of the firstmagnetic field within the second region. In certain implementations, thesecond magnetic field is generated via magnetic induction by causing theelectric current (e.g., generated by the at least one fourth circuit240) to flow in a path bounding the second region. For example, theelectric current can flow along the at least one third circuit 230(e.g., cancellation coil 236), with the second magnetic field within thesecond region (e.g., bounded by the cancellation coil 236) in oppositionto the first magnetic field along a direction substantiallyperpendicular to the cancellation coil 236. In certain implementations,the second magnetic field is configured to destructively interfere withat least a portion of the first magnetic field within the second region.For example, the second magnetic field can substantially totallydestructively interfere with the first magnetic field substantiallyperpendicular to a plane of the cancellation coil 236 in the secondregion (e.g., substantially complete cancellation of the Z component ofthe net magnetic field).

FIGS. 6A-6B schematically illustrate two example apparatus 600configured to reduce degradation of various types of low-power systemsthat are sensitive to magnetic fields in accordance with certainimplementations described herein. For example, certain implementationsof the apparatus 200 of FIGS. 2A-2G as described herein can reducedegradation of a low-power magnetic induction data transfer link due toa nearby high-power magnetic induction power transfer link.

The apparatus 600 comprises magnetic induction power transfer circuitry610 (e.g., at least one first circuit 210) configured to generate aninduction power transfer magnetic field 612 (e.g., the firsttime-varying magnetic field 212). The apparatus 600 further comprises atleast one circuit 620 (e.g., at least one second circuit 220) that issensitive to the induction power transfer magnetic field 612. Theapparatus 600 further comprises protection circuitry 630 (e.g., at leastone third circuit 230) configured to generate a protection magneticfield 632 (e.g., the third time-varying magnetic field 232) in responseto an electric current 642 (e.g., the time-varying electric current242). The protection magnetic field 632 is configured to at leastpartially protect the at least one circuit 620 from the induction powertransfer magnetic field 612. The apparatus 600 further comprisescircuitry 640 (e.g., the at least one fourth circuit 240) configured togenerate the electric current 642 in response to the induction powertransfer magnetic field 612 or in response to a signal indicative of theinduction power transfer magnetic field 612. In certain implementations,the at least one circuit 620 comprises at least one antenna 224 of adata transfer link (e.g., as described above with regard to FIGS.2A-2G). As schematically illustrated in FIG. 6A, the circuitry 640 canbe separate from the magnetic induction power transfer circuitry 610. Asschematically illustrated in FIG. 6B, the circuitry 640 can comprise atleast a portion of the magnetic induction power transfer circuitry 610.

In certain implementations, the at least one circuit 620 comprises asensor in various contexts (e.g., medical devices; consumer devices; IoTdevices; vehicles) that is sensitive to interference from the inductionpower transfer magnetic field 612 of the magnetic induction powertransfer circuitry 610 of the device. For example, the sensor can be amicrophone of an auditory prosthesis device or of any other device(e.g., consumer device; IoT device) in which the microphone isvulnerable to magnetic interference from the magnetic induction powertransfer circuitry 610 of the device.

It is to be appreciated that the implementations disclosed herein arenot mutually exclusive and may be combined with one another in variousarrangements. In addition, although the disclosed methods andapparatuses have largely been described in the context of conventionalcochlear implants, various implementations described herein can beincorporated in a variety of other suitable devices, methods, andcontexts. More generally, as can be appreciated, certain implementationsdescribed herein can be used in a variety of implantable medical devicecontexts that can benefit from a signal pathway between the stimulationassembly and the recipient during implantation (e.g., insertion) of thestimulation assembly.

Language of degree, as used herein, such as the terms “approximately,”“about,” “generally,” and “substantially,” represent a value, amount, orcharacteristic close to the stated value, amount, or characteristic thatstill performs a desired function or achieves a desired result. Forexample, the terms “approximately,” “about,” “generally,” and“substantially” may refer to an amount that is within ±10% of, within±5% of, within ±2% of, within ±1% of, or within ±0.1% of the statedamount. As another example, the terms “generally parallel” and“substantially parallel” refer to a value, amount, or characteristicthat departs from exactly parallel by ±10 degrees, by ±5 degrees, by ±2degrees, by ±1 degree, or by ±0.1 degree, and the terms “generallyperpendicular” and “substantially perpendicular” refer to a value,amount, or characteristic that departs from exactly perpendicular by ±10degrees, by ±5 degrees, by ±2 degrees, by ±1 degree, or by ±0.1 degree.

The invention described and claimed herein is not to be limited in scopeby the specific example implementations herein disclosed, since theseimplementations are intended as illustrations, and not limitations, ofseveral aspects of the invention. Any equivalent implementations areintended to be within the scope of this invention. Indeed, variousmodifications of the invention in form and detail, in addition to thoseshown and described herein, will become apparent to those skilled in theart from the foregoing description. Such modifications are also intendedto fall within the scope of the claims. The breadth and scope of theinvention should not be limited by any of the example implementationsdisclosed herein, but should be defined only in accordance with theclaims and their equivalents.

1. An apparatus comprising: at least one first circuit configured togenerate a first time-varying magnetic field for magnetic inductionpower transfer to a device; at least one second circuit configured togenerate and/or receive a second time-varying magnetic field formagnetic induction data transfer to and/or from the device; at least onethird circuit configured to generate a third time-varying magnetic fieldin response to a time-varying electric current, the third time-varyingmagnetic field configured to at least partially inhibit degradation ofsaid data transfer from the first time-varying magnetic field; and atleast one fourth circuit configured to generate the time-varyingelectric current in response to a received portion of the firsttime-varying magnetic field or in response to a signal indicative of thefirst time-varying magnetic field.
 2. The apparatus of claim 1, whereinthe at least one second circuit comprises at least one antenna and theat least one third circuit comprises at least one cancellation coilbounding a region containing the at least one antenna.
 3. The apparatusof claim 1, wherein the at least one fourth circuit comprises at leastone pick-up coil in series electrical communication with the at leastone third circuit, the at least one pick-up coil configured to passivelygenerate the time-varying electric current via magnetic inductionresulting from the received portion of the first time-varying magneticfield.
 4. The apparatus of claim 3, wherein the at least one firstcircuit comprises at least one power transfer coil having a firstprojection in a projection plane, the at least one pick-up coil having asecond projection in the projection plane, the second projection withinthe first projection.
 5. The apparatus of claim 3, wherein the at leastone first circuit comprises at least one power transfer coil having afirst projection in a projection plane, the at least one pick-up coilhaving a second projection in the projection plane, the secondprojection outside the first projection.
 6. The apparatus of claim 4,wherein projections of the at least one second circuit and the at leastone third circuit in the projection plane are outside the firstprojection.
 7. The apparatus of claim 6, wherein the at least onepick-up coil comprises a plurality of pick-up coils in series electricalcommunication with the at least one third circuit.
 8. The apparatus ofclaim 1, wherein the at least one fourth circuit comprises at least onesensor coil and control circuitry in series electrical communicationwith the at least one third circuit, the at least one sensor coilconfigured to passively generate a sensor signal via magnetic inductionresulting from the received portion of the first time-varying magneticfield, the control circuitry configured to respond to the sensor signalby actively generating the time-varying electric current.
 9. Theapparatus of claim 1, wherein the apparatus comprises an external firstportion of a medical system and the device comprises a second portion ofthe medical system implanted on or within a recipient.
 10. The apparatusof claim 9, further comprising a housing containing the at least onefirst circuit, the at least one second circuit, the at least one thirdcircuit, and the at least one fourth circuit, the housing configured tobe positioned externally to the recipient at least during said powertransfer and said data transfer.
 11. The apparatus of claim 9, whereinsaid power transfer and said data transfer are transcutaneous.
 12. Theapparatus of claim 9, wherein the medical system comprises an auditoryprosthesis system.
 13. A method comprising: transferring power via afirst magnetic induction link in a first region; transferring data via asecond magnetic induction link in a second region, said transferringdata simultaneous with said transferring power; generating an electriccurrent indicative of a first magnetic field from said first magneticinduction link; and in response to the electric current, generating asecond magnetic field in the second region in opposition to at least aportion of the first magnetic field within the second region.
 14. Themethod of claim 13, wherein generating the second magnetic fieldcomprises causing the electric current to flow in a path bounding thesecond region.
 15. The method of claim 14, wherein generating theelectric current comprises using the first magnetic field tomagnetically induce the electric current.
 16. The method of claim 14,wherein generating the electric current comprises magnetically inducinga sensor signal indicative of the first magnetic field and usingcircuitry to generate the electric current in response to the sensorsignal.
 17. The method of claim 13, wherein the second region is withinthe first region.
 18. The method of claim 13, wherein the second regionis separate from the first region.
 19. The method of claim 13, whereinthe second magnetic field is configured to destructively interfere withat least a portion of the first magnetic field within the second region.20. An apparatus comprising: magnetic induction power transfer circuitryconfigured to generate an induction power transfer magnetic field; atleast one circuit that is sensitive to the induction power transfermagnetic field; protection circuitry configured to generate a protectionmagnetic field in response to an electric current, the protectionmagnetic field configured to at least partially protect the at least onecircuit from the induction power transfer magnetic field; and circuitryconfigured to generate the electric current in response to the inductionpower transfer magnetic field or in response to a signal indicative ofthe induction power transfer magnetic field.
 21. The apparatus of claim20, wherein the at least one circuit comprises at least one antenna of adata transfer link.
 22. The apparatus of claim 20, wherein the at leastone circuit comprises a microphone sensitive to interference from theinduction power transfer magnetic field.